Analysis | Main Methods of Natural Gas Desulfurization

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As a clean energy source, natural gas is in growing demand. However, many gas wells contain hydrogen sulfide during extraction; this substance can cause corrosion of equipment and pipelines, pollute the environment, and be harmful to human health, thereby affecting the collection, processing, and use of natural gas. With the advancement of science and technology, the widespread use of natural gas desulfurization technologies has effectively addressed these issues, but at the same time, the costs associated with natural gas purification have also increased accordingly. There are many natural gas desulfurization technologies, and it is necessary to select the optimal one in order to achieve the best results with minimal investment. This article provides a brief overview of two desulfurization technologies, analyzes their advantages and disadvantages, and offers references. 1 Introduction At present, the main desulfurization technologies used in industrial production both domestically and internationally fall into three categories: dry (physical) desulfurization, biological desulfurization, and wet desulfurization. Wet desulfurization includes absorption methods and wet oxidation methods. The chemical absorption method, represented by alcohol amine absorption, has been widely used in industry to transfer H2S from the gas phase into the liquid phase, thereby purifying the gas. Biological desulfurization technology oxidizes H2S into elemental sulfur and H2SO4 under micro-oxygen conditions; however, this technology is not yet mature. Dry desulfurization technologies include the iron oxide method, activated carbon method, molecular sieve method, ion exchange method, membrane separation method, biochemical method, etc. At present, the dry pressure swing adsorption technology is the most widely used for small-scale natural gas desulfurization in industry; it features full computer control and automatic operation, and it is also capable of automatically shutting down faulty towers, thereby ensuring long-term safe operation. 2 Introduction to Desulfurization Methods and Comparison of Advantages and Disadvantages 2.1 Introduction to Desulfurization Methods （1）Amorphous hydroxyl iron oxide (dry method). Features: It boasts high desulfurization accuracy, high sulfur capacity, good strength, and the ability to operate unattended. It is widely used for the removal of H2S from natural gas, syngas, biogas, coal gas, shale gas, and various chemical materials containing sulfur ； Amorphous hydroxyl oxidation desulfurization is a reactive desulfurization method; it does not allow for control over the degree of desulfurization. It is a type of purification process, and as the desulfurizing agent becomes saturated and the desulfurization tower is penetrated, the desulfurization efficiency drops significantly, and the H2S content in the purified natural gas rises sharply. Therefore, it is necessary to replace the desulfurizing agent promptly. 　　Reaction mechanism: FeOOH + 2H2S → FeSSH + 2H2O; Operating sulfur capacity: ≥ 35% (W); Main equipment: 1 pretreatment separator, 1 skid-mounted desulfurization unit. 　(2) Composite desulfurizer (R-X) (wet process). Feature: The composite desulfurization agent system reacts in the absorption tower with organic sulfur compounds such as H2S and thiols to form stable sulfides, thereby creating a concentrated liquid of the desulfurization agent ； After entering the regeneration tower, the rich liquid mixes thoroughly with air, and under the action of the composite catalyst it is rapidly regenerated to produce sulfur, while the lean liquid is recycled ； It features fast response speed, good selectivity, stability, and low corrosiveness; however, it requires human supervision. 　　Reaction mechanism: R-X (composite desulfurizer) + H2S → R-HS-HX (absorption reaction); R-HS + HX + O2 → R-X-H2O + S (regeneration reaction). Working sulfur capacity: 30% to 50% (W). Main equipment includes absorption towers, regeneration towers, sulfur capture tanks, lean liquid pumps, blowers, flash tanks, make-up water tanks, gas-liquid separators, and sulfur storage facilities. 2.2 Comparison of Advantages and Disadvantages of Desulfurization Methods Through comparison, the wet oxidation method offers high desulfurization efficiency, as it can convert H2S directly into elemental sulfur. However, finding a desulfurizing agent that is inexpensive, efficient, easy to regenerate, simple in composition, and stable represents a challenge for the development of this method. The wet process has a high desulfurization load, complex process flows and auxiliary systems, high investment costs, high energy consumption, and high personnel management costs. The wet flue gas desulfurization absorption method is not discussed in detail in this paper. Essentially, the absorption method serves to concentrate H2S present in the gas. However, this process itself entails operational difficulties such as corrosion, solution degradation, and foaming. The dry desulfurization process offers advantages such as a simple process flow and auxiliary systems, a high degree of modular design, small floor space, ease of relocation, great operational flexibility, high desulfurization efficiency, low energy consumption, and low investment costs; it is particularly suitable for precise gas desulfurization. Most dry-process methods utilize solid scavengers to absorb or transform hydrogen sulfide into elemental sulfur or to form other solid compounds. 3 Conclusion 　　Through the comparison of the advantages and disadvantages of the two desulfurization methods discussed above, it is evident that existing desulfurization technologies need to continue to evolve and improve alongside scientific advancements in order to meet the current demands for natural gas purification. Natural gas extraction, storage, and transportation also contribute to the continuous improvement of existing desulfurization technologies, thereby achieving better results. There are various types of desulfurization technologies, but based on production requirements, dry desulfurization methods should be preferred as much as possible. These methods not only require less energy but also generate less pollution, thus helping to reduce costs. Reducing energy consumption, simplicity of operation, and low operating costs are the directions in which desulfurization technologies will continue to develop based on the current situation.